move code from packet.hh to packet.cc and packet_impl.hh

move code from packet.hh to packet.cc and packet_impl.hh
fix very annoying not-compiler bug

arch/sparc/regfile.hh:
    You have not included an out-of-class definition of your static members. See [9.4.2]/4 and about a billion gcc bug reports.
    If statements get around the problem through some magic, and than seems nicer that putting a definition of them in a c file
    somewhere.
cpu/simple/cpu.cc:
    get() and set() do the conversion now
dev/io_device.hh:
    need get() and set() defentions in all the devices
mem/packet.cc:
mem/packet.hh:
    move code from packet.hh to packet.cc
mem/physical.cc:
    packet_impl needed for templated packet functions

--HG--
extra : convert_revision : 6c11842aa928d9af7b4cabe826306fe1fe09e693